Advice on winning over parents for another pet?

[puppyrjjkm]

So one of my dad's manager has a 10 yr old paint mare that they are trying to get rid of for a mere $500! She spooks a lot, so it's not much fun to ride her. I would LOVE to get her, try to train her, and eventually and breed her (since she's papered), but we already have 3 horses who are extremely spoiled, but we don't ride a lot, but they still get a lot of attention. Any ideas on how can I encourage dad to get her?

[weluvbettas]

try and say horses do better in groups of 4 or more. That might win him over.